This invention relates to an engine combustion chamber and air intake device and more particular to an improved cylinder head and porting arrangement for an internal combustion engine.
The use of multiple intake valves for internal combustion engines is well known as an expedient for improving engine performance. Although four valve per cylinder engines (using two intake valves per cylinder) are common, there is an advantage to employing three intake valves and two exhaust valves for a total of five valves per cylinder. However, when five valves per cylinder are employed it is difficult to maintain low combustion chamber surface areas and high compression ratios. The reason for this is that the valve placement and the requirement to clear the head of the piston and permit adequate valve opening give rise to difficulties in obtaining the low combustion chamber surfaces and volumes necessary to achieve high performance and high compression ratios. As is disclosed in my U.S. Pat. No. 4,660,529 entitled 4-CYCLE ENGINE, issued Apr. 28, 1987 and now reissued as RE 33787 on Jan. 7, 1994, it is possible through placement of the intake valves as generally disclosed in that patent to obtain high compression ratios and still utilize five valves per cylinder.
It is a principal purpose of this invention to provide an improved combustion chamber configuration that permits still further increases in the compression ratio without increasing the likelihood of knocking.
It is a further object of this invention to provide an improved combustion chamber configuration and intake port arrangement for a five valve per cylinder engine.
When using multiple valves it is the common practice to provide a pair of valves serving related ports that are disposed on one side of a plane containing the axis of the cylinder bore and wherein the valves reciprocate about reciprocal axes that are disposed at an acute angle to this plane. In order to increase the amount of valve lift without decreasing the compression ratio it has also been the practice to incline the valve stems and associated ports to a plane that is perpendicular to the first-mentioned plane and which also passes through the cylinder bore axis. The valves are disposed at opposite acute angles to this plane. As a result of this construction, when the valves serve the intake function, the flow which enters the chamber through the individual valves will tend to intersect in the cylinder bore. This has certain disadvantages. Specifically, it is not always possible to provide the desired flow pattern in the cylinder bore and interfering turbulence may occur.
The use of two intake valves disposed as in the preceding paragraph is also used in combination with engines having three intake valves per cylinder. The two valves having the disposition disclosed form side intake valves and a center intake valve is disposed between these two side intake valves and closer to the outer periphery of the cylinder bore on the side opposite the first plane. Again, this can result in undesired air flow in the combustion chamber and particularly turbulence or interference in the air flows from the individual intake passages.
It is, therefore, a further principle object of this invention to provide an improved engine air intake device.
It is a further object of this invention to provide an improve valve placement for an engine wherein large valve lifts can be accomplished without reducing the compression ratio and without causing interfering flow between the individual intake passages.
It is a still further object of this invention to provide an improve valve and associated passage arrangement for the cylinder head of an internal combustion engine.
When multiple valves are employed per cylinder in an engine, the construction of the cylinder head and valve actuating mechanism tends to become rather complicated. This can give rise to other problems such as problems in correctly locating the fastening hold-down bolts for the cylinder head.
That is, it is desirable to provide substantially uniform spacing around the cylinder bore for the cylinder head hold-down bolts and with multiple valve arrangements this can be at time difficult.
It is, therefore, a still further object of this invention to provide an improved hold-down bolt pattern for the cylinder head of a multiple valve internal combustion engine.
It is a still further object of this invention to provide an improved bolting arrangement for such an engine.
The valves are normally operated by one or, more frequently, two overhead mounted camshafts. These camshafts may be journaled directly in the cylinder head or in components which form a portion of the cylinder head assembly. This requires a provision of additional bearing caps for journaling the cylinder head and at times the bearing arrangement and hold-down fasteners for the bearing caps can interfere with or obscure the hold-down bolts for the cylinder head itself.
It is, therefore, a still further object of this invention to provide an improved hold-down arrangement for a cylinder head of an overhead camshaft internal combustion engine.
It is a further object of this invention to provide an improved hold-down arrangement for the bearing caps of overhead mounted camshafts and the cylinder head of the engine wherein the hold-down fasteners can be conveniently formed and machining operations are simplified.
Because of the problems mentioned in connection with the complexity of multiple valve overhead valve cylinder heads, it has been at times the practice to employ a cylinder assembly that is made up of a number of castings that are secured to each other. Of course, as the number of pieces increases, the bolting arrangement, machine and cost of the cylinder head can become larger.
It is, therefore, a still further object of this invention to provide an improve cylinder head assembly for a multiple cam multiple valve engine wherein the cylinder head may be made of a single piece construction and yet afford ease of assembly and manufacturing.